Balloon locomotion



Jan. 28, 1969 A.ID. STRUBLE, JR

BALLOON LOCOMOTION Sheet Filed Jan. 4, 1965 Jan. 28, 196 9 E; JR 3,424,405

BALLOON LOCOMOTION Filed Jan. 4, 1965 Sheet 2 United States Patent Office US. Cl. 244-31 Int. Cl. B64b 1 40, 1 62 9 Claims This invention generally relates to lighter-than-air systems having locomotion control capabilities.

As is well known, it is often desired to gather weather data or to conduct military reconaissance above a relatively small portion of the earth. One inexpensive means of doing this is to employ a balloon as the vehicle for the data gathering equipment. However, since balloons are at the mercy of the prevailing winds, there is no assurance that by merely launching a balloon into the prevailing winds that it will eventually arrive over the desired area-and even if it does arrive over the desired area, there has heretofore been no satisfactory means for maintaining it in that approximate locality for any extended period of time.

The present invention pertains to a balloon system that having locomotion control capabilities can travel to and maintain itself over a target area for extended periods of time. My balloon system can conduct missions at altrtudes of 150,000 feet. Locomotion to a specific target is achieved through the selection of proper altitude to secure the required wind correction component. Relative wind data is furnished through a vertical array of wind sensors.

In order to effect vertical movement to get to the proper altitude, liquid hydrogen is preferably used in an expandable fashion for inflation; this technlque allows chmb control at a small fraction of the weight penalty associated with conventional ballasting. Hydrogen boil-ofi is contained in special pressure vessels (e.g. superpressure balloons), the latter forming part of the buoyance system.

The invention will be more clearly understood by referring to the drawings wherein:

FIGURE 1 is a perspective view of a balloon array in accordance with one embodiment of this invention;

FIGURE 2 is an enlarged view of the type of balloon system shown in FIGURE 1;

FIGURE 3 is a detailed view of the valve system shown in balloon C of FIGURE 2;

FIGURES 4 and 5 are perspective views of the balloon wind sensors in accordance with this invention; and D FIGURES 6, 7 and 8 are more or less diagrammatic type views illustrating various balloon arrays that can be employed in accordance with the teachings of this mvention.

FIGURE 1 shows an arrangement which includes balloons A, B and C. The entire array from point H to point Y may be 50,000 feet. The distance between balloons A and C may be only a few hundred feet or as much as 5,000 feet. D is a liquid hydrogen container which is ut1lized in controlling the ascent or descent of the balloon array. A plurality of wind indicators (e.g. W, W and W are disposed along the length of the array between polnts H and Y (e.g. at 1,000 foot intervals). H is a small balloon that primarily functions to keep the cable 21 above balloon A in a fairly taut condition.

One of the objectives of utilizing such an arrangement is to take advantage of the different wind conditions that may prevail at different altitudes so as to cause the ba lloons A, B and C to move in a desired direction or within a desired area. Suppose for example that it is desired to have the balloon array move in a northerly direction. If wind indicator W detects that there are strong winds at that altitude traveling in a northerly direction, it would obviously be desirable to cause the balloons A, B and C to rise to the same altitude as wind indicator W so that 3,424,405 Patented Jan. 28, 1969 they would be influenced by the winds prevailing there. Suppose, for instance, that wind indicator W is at an altitude of 100,000 feet and balloons A, B and C are all at about 80,000 feet, it will naturally be desirable for balloons A, B and C to rise to an altitude of 100,000 feet so as to take advantage of the northerly winds prevailing there. In order to make the balloons A, B and C rise to the level of wind indicator W a number of things can be done. First of all, increased amounts of lifting gas can be supplied to balloon A. If balloon B is a superpressured balloon then some of the superpressure gas in B can be valved off through conduit line 20 and into balloon A so as to cause balloon A to expand and thereafter rise. Alternatively, if balloon B does not contain any superpressured gas, then some gas can be bled off from liquid hydrogen container D into expandable balloon C, and as balloon C fills and expands it will provide suflicient lift to raise the entire array. The passage of gas between elements A, B, C and D is rather easily accomplished by means of conduits 20, 22 and 24.

At this point it should be mentioned that somewhere along the array between points H and Y there is preferably provided a small computer system which will govern the actions of the valving systems in the array. The computer can be programmed in advance of ascent or the computer can be controlled from a remote location on either land or sea, or even from a satellite.

Assume for purposes of illustration that the computer contained within the array has been programmed in advance and is independent of any ground intelligence system. When the computer receives information from the wind indicators that desirable directional winds are prevailing at a given altitude, the computer (together with solenoid valves) will then control the valves in the array so as to insure ascent of the balloons A, B and C to the altitude of the desired wind.

On the other hand, suppose that wind sensor W senses that there is a strong westerly wind at the altitude of W (and it is now desirable to have the array move in a westerly direction), this information is conveyed to the computer and the computer will then open appropriate valves in one or more of the balloons so that the balloons will descend to the level of W For instance, if valves are opened to vent gas from balloon A, balloon A will decrease in size and this will result in a decrease in lift and a descent of the entire array. If this method of venting will not achieve the desired degree of descent then a portion of the gas in lower lift balloon C may be vented into superpressure balloon B. Until the maximum of superpressure in balloon B has been reached (e.'g. 25%), balloon B will take up whatever gas is released from balloon C. When the maximum superpressure in balloon B is reached, then some of the gas within balloon B can be vented upwardly through nose of conduit line 20 to balloon A an dfrom balloon A outwardly into the atmosphere. By such means the balloons can be caused to descend to the level of W Accordingly, with the above-described three balloon array system (plus liquid hydrogen container D) it is possible to control the locomotion of the balloon system by sensing the direction and force of winds at various altitudes and then adjusting the lift capacities of the balloons so that the balloons will rise (or descend) to the most desirable altitude for directional locomotion.

Referring now to FIGURE 3, one type of valving system for achieving the previously described fiow of gases between the balloons is shown. In particular, the conduit 22 leading from balloon (not shown) C into balloon B is shown, together with its upper extension 22E. The flow of gas from conduit 22 upwardly through hose 22B is controlled by valve clamp 30. A lateral conduit 23 is provided between conduits 20 and 22 and the flow in conduit 23 is controlled by valve clamp means 32-32. The flow of gas from balloon B into hose conduit 20F and up through 20 is controlled by valve clamps 34 and 34'. Each of the clamp-type valves 30, 32-32 and 34-34 can be controlled manually by a person located within or below the balloon. Alternatively, those skilled in the art could readily provide automatic controls for such valves, or remote control means could be employed. Such means of control would be obvious to those skilled in the art.

With valve systems of the type described in FIGURE 3 it will be seen that it is possibe to direct and control the gas flow through the various balloons (both superpressured and non-superpressured). For instance, passage of gas from balloon C into balloon B can be achieved by allowing the gas to flow upwardly through hose 22 and out through hose extension 22E into the interior of balloon B (when the clamp valve 30 is open and the clamp valve 3232 is closed). The gas which enters balloon B will remain there until such time as clamp valve 34-34 opens to allow the gas to enter hose 20F and rise through hose 20 to balloon A.

In the event that clamp valve 30 is closed so that the gas will not flow upwardly from hose 22 and out of hose extension 22E, and if the clamp valve 32-32 is open then the gas will flow from conduit 22 through intermediate conduit 23 and then upwardly through conduit 20, thus bypassing balloon B.

FIGURE 2 shows an additional detail in accordance with this invention, wherein at least the lowermost balloon of the array is provided with a downwardly depending illumination deflector. In other words, for military reconnaissance purposes it might be desirable to have the sun or moon reflecting off of the surface of balloon C. FIG- URE 2 shows that the balloon C may be provided with an illumination deflector in the form of an irregularly shaped expanse of colored (e.g. blue) plastic or the like 60. This colored plastic could be supported by a plurality of support means 61, 63, 65 and 66. The plastic expanse 60 can be in the shape of a cloud and can also be partially inflated if this seems desirable.

FIGURE 2 also shows a down vent 20 A which is useful in connection with the venting of balloon A. FIG- URE 2 also shows more clearly an upper balloon H which is utilized to form a rather taut line 31 that is useful in connection with forming a general vertical support for the wind indicator W FIGURE 4 shows an enlarged view of one form of suitable wind indicator in accordance with this invention. It will first of all be noticed that a portion of the line, hose or conduit 70 between any two balloons (not shown) or below any balloon is surrounded by a vertical balance rod 72. Intermediate the ends of this rod there is provided a sensor and recorder means 74 of any well-known type. At approximately right angles to the vertical balance rod there is provided a horizontal rod 76 that terminates in a strain gauge 78 and a power supply 80. Adjacent the outer end of the strain gauge 78 there is provided a clamp which is connected to the lower end of rigid shaft 82. The upper end of rigid shaft 82 contains an inflated balloon 84. The sensor and recorder 74 is preferably mounted so that it is rather freely rotatable around vertical balance rod 72 and will be caused to be rotated by the direction of the prevailing winds. Once the sensor 74 and the rod 76 have been oriented in the direction of the prevailing winds the prevailing winds will exert a force against the balloon 84 so as to cause it to move away from a generally perpendicular position. In other words, the balloon 84 and its support shaft 82 will tend to move in the direction indicated by arrow A. In so moving, a force is registered on the strain gauge 78 and the magnitude of this force is transmitted to the sensor and recorder 74, which can be in turn transmitted to any other position of the array (or to remote stations) by electrical or electronic transmission means.

One of the novel features of the present invention is that the wind indicator assembly just described will at least partially compensate itself for the heights that are reached. In other words, at low altitudes the size of the balloon 84 will be relatively small and the force of the high-density, low-altitude air against the balloon, say at 20 miles an hour, will register a certain force on the strain gauge 78. At higher altitudes the density of the air will be considerably thinner, but since the balloon will automatically occupy a greater volume at elevated altitudes the decreased density in the air is at least partially compensated for (or counteracted) by the increased size of the balloon. It is believed that this type of wind indicator is novel and not heretofore known.

One difliculty with the type of wind indicator shown in FIGURE 4- is that the increase in altitude is a cubical function rather than a square function and there is accordingly some distortion of values with increased altitudes. FIGURE 5 shows an arrangement which is intended to overcome this distortion. The members 72A, 74A and 76A perform essentially the same functions as escribed previously in connection with elements 72, 74 and of FIGURE 4. The volumetric component in FIG- URE 5 is considerably different however, in that rather than being a spherical balloon such as 84 in FIGURE 4, in FIGURE 5 it consists of an accordion-like expansion arrangement. The expansion of the accordion-balloon 90 is controllably confined by the guide rails 92 and 94.

An extension 78A of the rod 76A is shown, the purpose of this extension 78A being to minimize any bending movement that might be caused by the force of the wind against the accordian balloon 90. The power supply is shown at A. An extensible wire 100 attached to a portion (preferably the top) of the accordion-ballon is also attached to a strain gauge (not shown) so that as the accordion-balloon 90 expands the strain gauge will register a corresponding force. Numberous other arrangements for attaching the strain gauge to accordion-balloon 90 could be provided.

A further feature in accordance with my invention is to provide a considerable length of cable '25 below the balloons, the purpose of such cable being to pick up static electricity from the air and thus provide power-electrical power-for the system. A high voltage and low amperage can be obtained in order to get some usable power. In FIGURE 1, P is a payload of instruments attached to the balloon array.

It will thus be seen from the specific embodiment illustrated in FIGURES l5 that the basic combination of components in accordance with this invention consists of at least one expandable balloon (or lift ballon) and at least one container within which gas can be 'maintained under superpressure (in either a liquid or gaseous form). The lift gas is preferably either hydrogen or helium.

FIGURE 6 illustrates the simplest combination of components in accordance with this invention. It consists of an expandable balloon 100, a container for gas under pressure 102 and a conduit 104 interconnecting balloon and container 102. Now let us suppose that the combination shown in FIGURE 6 is at 80,000 feet and it is desired to have it ascend to 100,000 feet. This can be accomplished by bleeding oflf a portion of the gas under pressure from container 102 into expandable balloon 100. This will cause balloon 100 to expand and rise. Conversely, if we desire the arrangement shown in FIGURE 6 to descend from 80,000 feet to 60,000 feet the gas within balloon 100 can be vented to the atmosphere to a limited extent and the entire array will descend to the desired altitude.

FIGURE 7 shows another generalized arrangement in accordance with this invention, comprising expandable balloons 106 and 108 and containers 110 and 112 for gas under pressure. Conduits 114, 116 and 118 interconnect the aforesaid components 106, 110, 108 and 112. With this arrangement, when we want to descend we can let gas out of the balloon 106 (i.e. vent it to the atmosphere) and as balloon 106 decreases in size the entire array will descend. Alternatively, in order todescend, we can let gas out of expandable balloon 108 and pass such gas into superpressure balloon 110. As soon as the volume of balloon 108 decreases the entire array will drop. In order to get the array of FIGURE 7 to rise we can do either of two things. First of all, we can let gas out of the superpressure container 112 and introduce it into the expandable lift balloon 108 so that the expansion of balloon 108 would cause the system to rise. Also, we could let gas out ofsuperpressure container 110 into expandable balloon 106, and an enlarged balloon 106 would cause the system to rise. Stabilization at any desired altitude may be achieved by suitable manipulation of the gas into and out of the lift balloons.

By using the above-described system it is possible to greatly conserve gas during ascending and descending operations. Of course, gas that is vented out of the tippermost expandable balloon in a vertical series is ordinarily not recovered and is lost.

FIGURE 8 is very similar to FIGURE 7 except that it shows a liquid hydrogen tank 120 at the bottom of the array. Initially the gas would simply bleed off from liquid hydrogen supply tank 120 in a nearly continuous manner and into balloon 124 (via conduit 122) which can be considered as a storage or superpressure balloon. By operating in this manner one does not have to throw away the bled off gas and at the same time the liquid hydrogen tank 120 does not become overpressured. Balloon 124 can, for instance, take up to as high as 25% overpressure (at a constant volume). Balloon 124 is therefore what is referred to as a superpressure balloon.

Now suppose that balloon '128 is an expandable lift balloon that is only partially filled and balloon 132 is another superpressure balloon similar to 124. Now further suppose that balloon 132 is initially in a rather limp or semi-full condition. Now if we want to ascend we merely let some gas out of superpressure balloon 124 (that is some of the excess superpressure gas) and pass it into balloon 128. As balloon 128 expands the entire array will start climbing. Once the desired altitude is reached and we want to stabilize at that altitude we can vent some of the gas from balloon 128 into superpressure balloon 132. Balloon 132 can actually be superpressured by the gas exiting from balloon 128 by having it rise up the conduit 130. Conduit 130 is preferably quite long. As the lift gas enters into balloon 132 (from conduit 130) it eventually doesnt change the actual volume of balloon 132 because this balloon is already full and the introduction of gas merely raises the pressure in balloon 132. However, balloon 128 now starts getting limp again due to loss of gas and the array will level off at the desired altitude.

Now, if we want to descend we can let more gas out of expandable balloon 128, which will decrease its volume and lifting power. The gas exiting from balloon 128 is preferably conducted into superpressure balloon 132 and balloon 132 therefore becomes even more superpressured. The entire array will then start downwardly. Now, when we want to level off again we can let some gas out of superpressure balloon 124 into expandable balloon 128 or we can let some gas out of superpressure balloon 132 into expandable balloon 136 and we will level off. In this latter case, if we let the gas pass from superpressure balloon 132 into expandable balloon 136 it will be seen that we have made multiple use of the gas that originated from the liquid hydrogen tank v120. In fact, it is possible to make several maneuvers (ascents and descents) with one increment of gas.

With a balloon array system of the type described above, it is possible to in effect orbit or position a payload (e.g. weather instruments or reconnaissance instruments) above a desired area of the earth. For example, if a computer system in the balloon array is associated with navigational equipment and it is desired to maintain a balloon system within a generally fixed location above a certain area of the earth, the wind sensors can detect at what altitude a favorable wind exists to get the balloon to the desired area and once the desired area is reached and that particular wind current would have a tendency to move the balloon system beyond the desired area, another wind sensor would sooner or later detect a wind going in the opposite direction and when the balloons were repositioned at the desired altitude, then the balloon array would go in the opposite direction until it approached a point where it was going out of the target area. At this time, the computers and navigational equip ment could instruct the sensors to locate another wind current that would take the array back over the target area.

The lift vehicle fabric requirements are strongly infiuenced by balloon design, superpressure and gross-lift capacity af the system. The fabric to be selected must demonstrate good physical characteristics such as (1) low Weight per unit area, (2) high strength to weight ratio, (3) low leakage constant, (4) no deterioration or aging due to ultraviolet radiation, (5) low cold brittleness temperatures, and (6) good tear strength and toughness.

A most attractive balloon material is a composite fabric utilizing either polyethylene or polypropylene in combination with a network of high-strength fibers. The strength member matrix can act either as a rip stop or as an integral load carrier.

Looking next to the question of the practicality of using very thin film balloon vehicles, the launching and severe weather conditions in the troposphere can be obviated by using a staged vehicle approach. For example, a rugged helium-filled first-stage of comparatively modest volumetric design can be used to effect the hazardous launch phases and to transit storms and areas of high windshears to an altitude of 40,000 to 70,000 feet. At this altitude, the second stage (i.e. shown in FIGURES l-8) is energized for the altitude mission; the first stage booster then returns to the ground. The first stage thus functions as a launching platform for the second stage.

The first stage booster could, of course, be recoverable. Sea basing is suggested as an immediate means for a secure launching and recovery site; sea basing would also supply a flexible base that could move with the demands of the weather and/or the mission.

Prior to final command release of the vehicle of this invention at altitude, weather data and target information would preferably be fed into the balloon guidance system from support vehicles such as an airplane or satellite. By the same token, after the vehicle has moved across the reconnaissance zone and can become active, weather information can be read out for the purpose of providing up-todate weather inputs to vehicles starting a mission. Several altitude vehicles could be orbited at a starting area on a standby basis and that once a reconnaissance run is started, the continual transit of vehicles over the area of concern will provide weather information and will allow effective forecasting.

Since the expected operational altitudes have very low absolute pressures, the flamability of hydrogen with air is improbable. The system of this invention can thus use hydrogen as the buoyancy gas and boil ofi liquid hydrogen for altitude control. The amount of maneuverability is a direct function of the proportion of gross weight that can be given to liquid hydrogen. This is analogous to the fuel percentage for a conventional aircraft. Further, the liquid hydrogen consumption is directly proportional to the square of the rate of climb or descent. Thus, if lower rates of climb or descent can be used, a larger number of cycles of altitude change can occur using the same weight of hydrogen. Liquid hydrogen storage for periods in excess of a month can be realized with low container weight and boil-oft compatible with the system demand.

It should be noted that a system designed for ascent to having three buoyancy chambers with sufficient reserve buoyancy gas and a fail safe ducting technique can still maintain a very respectable flight altitude even though one chamber completely fails; this is considered highly important in the case of a reconnaissance vehicle.

The conventional weight penalties for creating rates of climb and descent by dumping weight are replaced by the much more efficient technique of supplying additional buoyancy. Buoyancy versus weight jettison provides an improvement in the weight penalty by a factor of approximately 10.5. The technique of vertical gas cycling provides further weight improvements. As a consequence of these performance gains, the conventional problem of traversing the stratopause is obviated. The use of liquid hydrogen as the inflation gas must satisfy the problem of climb and level off gas requirements versus the gas container boil-off supply. Conversion and storage techniques are state-ofthe-art.

The special problem of maximum altitude zone penetration would require full inflation of all available volumes and the cycling of hydrogen gas vertically between units for climb and descent. Overpressuring of the units can effect very efficient altitude changes; proper cycling between balloons is very useful in the case where precise orbiting control is desired and for fast response in terminal guidance corrections.

With a vehicle system capable of directional locomotion, the provision of passive guidance error signals and payload commands must be satisfied. Using radio direction finder techniques, the vehicle system can obtain error signals and remain passive. It can also take line-of-sight bearings on pre-established ground transmitting stations located outside the area of concern. The possibility of satellite guidance and command links is also apparent.

The liquid gas containers mentioned in the above description can be constructed in various ways. However, the cryogenic containers set forth in my copending application Ser. No. 397,436 are preferred.

The lighter-than-air systems described above can be provided with various fail-safe features in the event of balloon envelope failure so that the failure of one balloon will not ruin the whole system. For instance, looking at FIGURE 3, strain gauges (not shown) could be placed approximately at points M and N and then interconnected in any suitable manner so that a differential reading would be obtained which would be an indication of the amount of gas pressure within the balloon. Now if the balloon fails (due to rupturing or the like) and all of the gas escapes there will be no differential reading on the strain gauges because there would no longer be any gas in the balloon. When this differential reading was zero (or low enough to indicate serious rupture of the balloon) this condition of the strain gauges could be caused to automatically and permanently close both valves 30-30 and 3434 and permanently open valve 32-32'with the result that the gas rising through conduit 22 would cross over through conduit 23 and then rise through conduit 20, with no loss of the gas in the conduits due to rupturing of one balloon. In other words, no further gas would be fed into the bad envelope by the conduits, and instead the gas would automatically go to the next higher good balloon. This arrangement would also permit the overloading of one or more of the good balloons located above a malfunctioning balloon so as to provide additional lift to keep the array near its original altitude.

FIGURE 9 illustrates a launcher balloon in accordance with this envelope. As shown the launcher balloon 120 is generally tubular in design having a central core or cavity 122. Cavity 122 has a lower axial extension 124 thereon and the extension is maintained in place by a plurality of shroud lines 126 that depend from the lower portion of the launcher balloon 120. In FIGURE 9 a balloon 128 is shown extending upwardly from the central cavity 122. The launcher balloon has an altitude capability of between about 40,000 and 70,000 feet.

The purpose of central cavity 122 is more clearly illustrated in FIGURE 10 wherein the central cavity is shown broken away. It will be seen that the central cavity 122 is adapted to house a plurality of packaged balloon units. For example a box is shown for an upper balloon 128 and a box 132 is shown for a lower balloon. There could be any desired number of balloons and any desired number of boxes to house the balloons. The various balloons are connected by conduits or cables 134. The lowermost balloon in a series of balloons is usually attached by cable means 136 to a payload 138 (e.g. instruments).

Each balloon within the cavity 122 is designed to sequentially rise upwardly through the cavity so that the entire balloon array is deployed in a gradual manner. Each balloon is preferably boxed 0r packaged with a plurality of rip seam panels 140 so that the lift gas within a balloon can pop the panels in a sequential manner as the balloon ascends. In this way the minimum amount of uninflated balloon envelope material is subjected to the adverse effects of any high altitude wind streams that might be encountered.

What is claimed is:

1. An untethered free-floating system comprising a plurality of gas containing chambers that are movable with respect to each other and that are interconnected to each other in a generally vertical array by means of elongated conduits, at least one of said gas chambers having a constant volume and at least one of said chambers having a variable volume, said system initially containing an excess of buoyancy gas each of said elongated conduits being longer than the maximum width of either of the chambers which it interconnects.

2. A system according to claim 1 which contains at least one superpressured balloon and at least one expandable balloon.

3. A system according to claim 1 wherein there are at least two superpressure balloons and at least two expandable balloons.

4. An untethered free-floating system comprising a plurality of gas containing chambers that are movable with respect to each other that are interconnected to each other in a generally vertical array by means of elongated conduits, all of said gas chambers comprising super-pressure balloons, said system initially containing an excess of buoyancy gas each of said elongated conduits being longer than the maximum width of either of the chambers which it interconnects.

5. An untethered free-floating system of lighter-thanair containers that have locomotion capabilities comprising: at least two expandable lift balloons and at least two superpressure balloons, said balloons being movable with respect to each other and interconnected by means of elongated conduits through which gas may pass from one balloon to another, said superpressure balloons each being positioned below a different expandable lift balloon each of said elongated conduits being longer than the maximum width of either of the chambers which it interconnects.

6. An untethered free-floating system according to claim 5 wherein a plurality of wind sensors are distributed along and below said balloon system in a vertical array to detect the wind velocities at the various altitudes.

7. An untethered free-floating system of lighter-thanair containers that have locomotion capabilities comprising a plurality of superpressure balloons that are movable with respect to each other adjacent pairs of, said balloons being interconnected to each other in a generally vertical array by means of an elongated conduit through which gas may pass from one balloon to another each of said elongated conduits being longer than the maximum width of either of the balloons which it interconnects.

8. A method for locomotion for an untethered freefloating and generally vertical array of balloons that are movable with respect to each other which method comprises: releasing said balloon array, determining the wind profile over a height of at least 5,000 feet, varying the buoyancy of the array to cause said balloon array to stabilize at the altitude of any desired wind level, and continuously repeating said procedure so that the freefloating balloon array will remain in the proximity of an area of concern.

9. A fail-safe system for an untethered free-floating vertical array of a plurality of balloons interconnected by elongated gas conduits, each of said elongated gas conduits being longer than the maximum width of either 15 the upward flow of gas through conduits to only con- 20 tinue if there is a properly functioning balloon somewhere thereabove.

References Cited UNITED STATES PATENTS 911,260 2/1909 Pennock 317-262 X 1,039,476 9/ 1912 Austin 244-33 1,486,399 3/ 1924 Trent 244-30 3,108,765 10/ 1963 Stone 244-3 1 3,179,962 4/1965 Shear et al. 9-8 3,217,536 11/1965 Motsinger et al. 73-189 3,229,290 1/ 1966 Fisher 244-98 X 3,229,517 1/1966 Smith 244-33 X FOREIGN PATENTS 4,433 8/ 1910 Great Britain. 137,014 1/1962 Russia.

OTHER REFERENCES Booda, L.: USAF Balloon Achieves Endurance Mark. An article in the magazine Aviation Week and Space Technology. p. 30. July 16, 1962.

MILTON BUCHLER, Primary Examiner.

T. MAJOR, Assistant Examiner. 

1. AN UNTETHERED FREE-FLOATING SYSTEM COMPRISING A PLURALITY OF GAS CONTAINING CHAMBERS THAT ARE MOVABLE WITH RESPECT TO EACH OTHER AND THAT ARE INTERCONNECTED TO EACH OTHER IN A GENERALLY VERTICAL ARRAY BY MEANS OF ELONGATED CONDUITS, AT LEAST ONE OF SAID GAS CHAMBERS HAVING A CONSTANT VOLUME AND AT LEAST ONE OF SAID CHAMBERS HAVING A VARIABLE VOLUME, SAID SYSTEM INITIALLY CONTAINING AN EXCESS OF BUOYANCY GAS EACH OF SAID ELONGATED CONDUITS BEING LONGER THAN THE MAXIMUM WIDTH OF EITHER OF THE CHAMBERS WHICH IT INTERCONNECTS. 